BAGHDAD  Cheering Iraqis dragged the charred bodies of four American civilians through the streets of Fallujah Wednesday, hanging two from a bridge over the Euphrates River and pulling apart the others, after insurgents ambushed the Americans' vehicle.

The sign reads: "Fallujah is the cemetery of the Americans;" one of the two SUVs hit burns in the background.

By Wathiq Khuzaie, Getty Images

In a separate incident, five U.S. soldiers were killed when a bomb exploded under their armored personnel carrier in Malahma, 12 miles northwest of Fallujah, a city where anti-American sentiment has resonated since the first day of the occupation.

The two attacks marked one of the bloodiest days this year for the U.S.-led coalition governing Iraq.

The attacks on the civilians, employees of a North Carolina firm, may have lasting impact because the violence produced horrific images of American bodies being abused and showed a new level of anti-American anger. Other civilians have died in recent attacks, but these are the first in which bodies have been mutilated.

Attacks on Americans in Iraq

A look at some of the deadliest attacks on Americans in Iraq since President Bush declared major combat operations over on May 1.

March 31: Bomb explodes under U.S. vehicle in Anbar province, killing five troops. At least four foreign nationals, including one American, are killed in a separate attack in Fallujah on the same day.

Nov. 2: U.S. Chinook helicopter carrying troops headed for leave is struck by missile and crashes west of Baghdad, killing 16 soldiers, wounding more than 20.

The searing images of dismembered bodies, captured by photographers and television cameras, revived memories of an American helicopter pilot being dragged through the streets of Mogadishu, Somalia, in 1993. Those gruesome pictures led to a decline in U.S. support for the mission in Somalia and the eventual withdrawal of U.S. troops from the African country.

The White House vowed that the United States would stay the course in Iraq.

Some analysts and historians said, though, that the photographs could test American resolve and support for the mission in Iraq. That probably was part of the attackers' motivation, they said. "What you're trying to do is create images," said Anthony Cordesman, a military expert at the Center for Strategic and International Studies.

News executives struggled with how to handle the images. Executives at ABC, CBS and CNN aired some of the footage on their evening newscasts, though only after careful review and a caution to viewers about its graphic content. "We have a responsibility to our audience to both show the face of war but to also be thoughtful editors and not simply put images out because they exist," said Jeffrey Schneider, an ABC vice president.

The violence in Fallujah started when guerrillas opened fire with rocket-propelled grenades and automatic weapons as the two civilian vehicles rolled through the city. The vehicles were set ablaze.

Fallujah police Maj. Assad al-Jumail said as many as 300 residents poured into the streets to celebrate and chant anti-American slogans. As flames roared from the vehicles' blackened hulks, some local residents pelted them with rocks and pieces of wood.

Jumail said the Americans' bodies were burned beyond recognition and were mutilated by some in the crowd.

"The mood is very hostile; the city is very tense," Jumail said. He added that the assaults were probably revenge for an incident last week in which four Iraqis were killed in the city during a search operation by newly arrived U.S. Marines.

Associated Press Television News pictures showed one man beating a charred corpse with a metal pole. Others tied a yellow rope to a body, hooked it to a car and dragged it down the street. Two blackened and mangled corpses were hung from a green iron bridge across the Euphrates.

"The people of Fallujah hanged some of the bodies on the old bridge like slaughtered sheep," resident Abdul Aziz Mohammed said. Some of the corpses were dismembered, he said.

Beneath the bodies, a man held a sign with a skull and crossbones and the phrase "Fallujah is the cemetery for Americans."

"This is the fate of all Americans who come to Fallujah," said Mohammad Nafik, part of the crowd surrounding the bodies.

APTN footage, which showed the charred remains of three slain men, quoted residents as saying some of the victims were wearing flak jackets and that there were weapons in the targeted cars. The pictures also showed a U.S. passport near a body.

"These are horrific attacks by people who are trying to prevent democracy from moving forward, but democracy is taking root," White House spokesman Scott McClellan said. He said the United States was holding fast to a deadline of June 30 for handing over power to a transitional Iraqi government.

The slain civilians were not identified pending notification of next of kin. All four were men who worked for Blackwater Security Consulting, a U.S. government subcontractor providing convoy security for food deliveries, the North Carolina company said. The company includes former Special Forces troops among its employees.

No military response

No U.S. troops or Iraqi police were seen in the area for several hours after the attack, but a U.S. fighter jet roared overhead, prompting the crowd to scatter.

Near Fallujah, a roadside bomb killed five U.S. soldiers when an armored personnel carrier that was part of an Army convoy rolled over it. The blast left a deep crater.

More than 290 U.S. soldiers have been killed in Iraq by hostile fire since May 1, when President Bush declared an end to major combat operations.

The attacks came after a period in which insurgents and terrorists seemed to be moving away from strikes against the military and toward so-called soft targets such as civilians. But Wednesday's attacks appeared to be evidence that attackers were capable of operating on both fronts simultaneously.

The number of attacks on U.S. forces had been steadily declining until this month. In February, 12 U.S. soldiers died because of hostile fire, a decline from a peak of 70 hostile fire deaths in November. But U.S. military fatalities have mounted in March, climbing to 36.

Civilians have also come under fire in Iraq, and several dozen have been killed. There are thousands of civilians operating in Iraq, including contractors working on reconstruction efforts, missionaries and business people. Last month, two Army civilian contractors were killed south of Baghdad. A week later, four members of a Virginia-based missionary group were slain in northern Iraq.

Brig. Gen. Mark Kimmitt told reporters here that the U.S. coalition would not change the daily dispatch of civilian contractors to the Fallujah region, a stronghold of former dictator Saddam Hussein.

"Coalition vehicles go through there every day," Kimmitt said. "(The military) is determined to establish order."

Coalition officials had predicted an increase in all types of attacks as insurgents attempted to disrupt efforts to transfer sovereignty to Iraqis by June 30.

It is difficult to determine whether the attacks symbolize a renewed guerrilla offensive or simply reflect problems characteristic of Fallujah, long a hotbed of Saddam sympathizers. The region is a patchwork of tribes deeply suspicious of outsiders.

The city of 176,000 and the surrounding Anbar province have resisted U.S. efforts to pacify the area, which is at the heart of the so-called Sunni Triangle. Sunni Muslims, a minority sect, historically dominated government in Iraq.

Residents of Fallujah's working-class community of low-slung buildings and narrow streets are open about their hostility toward Americans.

"I have zero hope," Adnan Dhahi Ibrahim, 47, the city's deputy manager, said in an interview last week. "The best hope is that Americans should leave the country."

The collective view of the city is expressed on an Arabic banner strung on the wall outside City Hall: "On the one-year anniversary of Iraq's occupation, Fallujah is demanding to expedite the transfer of power to Iraq."

Perhaps more than anyone, Gen. Aboud al-Issaway, Fallujah's police chief, understands the fragile nature of security here. More than 20 people died in a recent attack on his police headquarters. Part of the building's façade still carries small craters from the barrage of rockets and bullets.

"Fallujah people are the best fighters," al-Issaway said in an interview several days before the attacks. "The stronger they are hit, the greater the reply."

Al-Issaway may be one of the few who says he believes the Americans have a role here and should not abandon Iraq. "Nobody is saying that Americans should pull out of Iraq. But they should stay away from our city center. For each dead Iraqi, America gets 70 Fallujah enemies."

"Fallujah remains one of the cities in Iraq that just doesn't get it," Kimmitt said. He dismissed as misleading any comparison between the Fallujah and Somalia incidents.

"This is a tragedy...four families will be getting a dreadful knock at the door today," he said.

But he vowed that the military would not retreat from the city. Marines recently arrived in the area to replacing the outgoing 82nd Airborne Division.